LGPL-3.0 dependency in pymeeus library

I just scanned the dependencies for Prophet, and found that the Pymeeus package used by the convertdate package is licenced under the LGPL-3.0 License.

Is there a possible replacement we could make here?

```
|-- prophet >=1.0.0
| |-- convertdate >=2.1.2
| | |-- pymeeus >=0.3.13,<=1
```

[Pymeeus Licence](https://github.com/architest/pymeeus/blob/master/LICENSE.txt)